[atoyota4x4]

Well, I will try and keep this as short as possible. We purchased our 2000 Intrigue in November of 2004. That December I noticed the temp gauge acting funny on a small road trip one night. Read online about GM having a redesign on the thermostat. I replaced it with the new GM part number and all was fine up until this past 06-07 winter here in Kentucky. When the temp dropped below freezing the thing would climb to the "H".

My wife started telling me about a noise she would hear every once in a while. She said it sounded like a bag slapping underneath the car. I would drive it and could not get it to do it until one night she came home and said it did it on they way home. I immediatly got in and drove it around. Well, I soon noticed the temp gauge climbing to the "H" and when it got above 3/4 I heard "The Noise". It was a popping sound which I heard on future occasions only when it got above 3/4. I assumed this to be water hitting the hot block and vaporizing. Like a stuck thermostat or something. Anyway, she never noticed the temp gauge rising when the noise would occur. Well, the Red light on the gauge has never come on, and yes it works because I see it on start up.

So I figure its a pain in the butt to replace the thermostat but oh well, I will. I do that, but unfortunatly that did not solve the problem. So then I think its air trapped in the system. I gamble and take it to my local Valvoline Instant Oil change and have them flush the coolant, thinking this will remove any air. Well, whether it did or didn't, that did not work either. Still overheating on very cold days. Other days in the 40s or 50s, it would run normal all day long.

Next, I take it to a radiator specialist. They cannot get it to overheat, of course. because of this, they cannot try anything. So I put another T-stat on it thinking, maybe I got a bad "new" one. This time I purchase a aftermarket one. Got it in, it still would overheat.

By this time I'm ready for a trip to the dealer. Well the next morning after changing the last t-stat, I take it to my local GM dealer. On the way I notice a antifreeze smell. After about 12 miles into my trip I stop the car to check and oops, I forgot to tighten the radiator cap down. So I lost a little fluid but not much but on the way to the dealer it was overheating. I get there, tell them what the deal is and later that afternoon, I get the call from the actual mechanic. "Mr Seebold, I have driven your car over 40 miles and it has yet to over heat. Its been idling here at the shop for 1-2 hours and not once showed signs of overheating. He checked with his computer stuff and the gauge is fine and it does not indicate a blown head gasket. Oh, the radiator specialist also check for blown head gasket and they to agreed.

Well, from that time on which I believe was in late Jan or early Feb we had the same types of below freezing temps and the car did not over heat once. Unbelievable!! Did leaving the cap loose on the radiator have anything to do with it running normal up until summer? I don't know

Well, now that its gotton hot, it wants to do it again. Again, not all the time, just whenever it feels like it. I cannot tie it to anything in the world. Sometimes the A/C makes it run hot. Shut that off, it will drop back to normal, then it might get hot again with that off. Once on a recent trip in 90 degree weather it started running hot with the A/C on. I told my wife, I'm not shutting it off and if it blows up, it blows up. Well it ran hot (when I say hot, I mean between 1/2 and 3/4) for a while and then started running normal. I have no idea why.

All the fans work at the appropriate times, it has the right amount of coolant and I cannot find anything obstructing air flow.

I would love to find the answer to this mystery. I have found multiple people that experienced this same exact problem on their 3.5L, but they never said what the end result was that was causing it. Guess they would just trade it in or sell it.

At this point, I game to try anything as long as its not exspensive.